From my experience panda gobies actually have a pretty good survival rate but the issue is that they come in so tiny, you'll never see them again. I put one in my RSM and thought for sure it had died but it was alive and kicking. They literally arrive to us at about 1/2" in length and don't grow a whole lot.
Clown gobies are great but the trick is to get a healthy one. I've seen a lot of trouble with the green clown gobies arriving completely emaciated...pinched bellies like you wouldn't believe. But if you can get one in that either doesn't have a pinched belly or is recovering from it, they are actually quite cool. I haven't had as much trouble with yellow clown gobies having pinched bellies. As far as clown gobies go, I totally love these fish but in my experience yellow clowns are more of a pest to SPS than greens. The yellow clowns that I have had have stuck to one coral, hanging out in it's branches constantly...which irritates the polyps a bit. I had a healthy acro go downhill because of a yellow clown goby. The green clown gobies tend to dart around from coral to coral so they aren't as bad on any individual coral. Again, this is just my experience. Some people say they'll nip SPS flesh off to lay their eggs. I never had that happen either.
All the clowns basically dart in and out of corals, not really being much of a water column swimmer. Pandas are far more reclusive than yellows or greens.
There's a new one I've been seeing...black clown gobies. They are neat! Jet black!
Anyway...that help?
Oh and one more thing...tiny gobies are a bit more susceptible to ich in my opinion because it takes fewer parasites to actually make them very ill. Think about it...if 10 ich parasites infect a yellow tang versus a yellow clown goby, the difference to the fish will be HUGE. I had an ich outbreak and all my tiny gobies perished in the main display. However, I had an ich outbreak in the RSM and hooked up a UV sterilizer and they all made it through, no problem.
Disclaimer: these ich outbreaks were about 10 years apart. Don't want anyone thinking I'm constantly having ich outbreaks.